Decontamination apparatus and method

ABSTRACT

Apparatus and method for control of hazardous particulates such as asbestos during removal of these materials. Asbestos was applied as insulation and wall finish in many buildings before the dangers of particulate asbestos were recognized. A substantially airtight containment is provided around the affected work space. An accessway is provided to allow access for persons tools equipment, and materials. A filtration machine is provided to induce air flow into the work space, desirably at all times during the removal process. Air discharged from the work space through the filtration machine is filtered. All air passages into the work space are filtered to avoid introduction of contamination from the outside. Filtered air passages are provided to sweep the work space to reduce exposure of the workers to the hazardous materials. In case of failure to maintain air flow during the removal process, there is containment of the hazardous materials, since all passageways connecting the contaminated work space to the outside are filtered. High efficiency Particulate Air (HEPA) filters may be used.

BACKGROUND OF THE INVENTION

This invention relates to the removal of asbestos which has been appliedfor insulation and other purposes. Asbestos was used extensively forinsulation in building construction and other purposes in the past. Myinvention also applies to removal of other hazardous particulate.Serious health hazards have now been associated with breathingparticulate asbestos. Asbestos is being removed from many buildingswhere it was applied as part of wall finishes and insulation againstheat transfer. Fibers 5 microns or greater in length and with an aspectratio of 3:1 are addressed in environmental standards. A phase contrastoptical microscope with about 440 magnification is used to count fibers.Requirements for an area to be undisturbed for 24 hours to allow fibersto settle does not provide for control of particulate matter in a workspace where asbestos or other hazardous particulate matter is beingremoved. My invention does provide for control of particulate in a workspace.

The description of my method and apparatus is directed to controlasbestos particulates; however, my method and apparatus can be used tocontrol other hazardous particulates.

Air filtration systems of many designs have been patented and others areavailable commercially. Vacuum flow collectors are availablecommercially. Vacuum flow collectors are in use to collect particulatessuch as graphite dust generated in performing machining operations ongraphite work pieces. Filters then remove the particulates before theair is discharged to the outside.

U.S. Pat. No. 4,604,111 to Anthony Natale describes method and apparatusfor controlling particulate matter in asbestos removal projects, forexample: Natale provides an enclosed space, air flow establishing anegative air pressure, air flow entry, filtered air discharge, and sealof the air flow entry in case of the loss of the negative air pressure.Natale teaches the use of polyethylene plastic film flag seals to closeair flow entryways to the contaminated work space.

A polyethylene plastic flap acting as a check valve allowing air flowthrough a doorway can be seen as not providing an effective seal of thedoorway under condition of the loss of vacuum in the work space.Movement of contaminated air out of the work space can be expected evenwith low air flows caused by wind or artificial air circulation byadjacent air conditioning or ventilation blowers.

U.S. Pat. No. 2,710,574 to H. E. Runion describes a system for removingmist or particulates form an enclosure. U.S. Pat. No. 4,255,169 to R. M.Leliaert describes an energy conservation system of recirculating air toan industrial process with intermediate removal of dust or dirt. U.S.Pat. No. 4,175,934 to Arnold Lang discloses a "Clear Air Device"utilizing HEPA (High Efficiency Particulate Air) filtration to cleanseair for a positive pressure clean air room. U.S. Pat. No. 3,498,032,incorporated here by reference, describes a High Efficiency ParticulateAir filter as covered by U.S. Federal Standard 209a.

A number of techniques have been developed to control particulatecontamination during the removal of asbestos and other hazardousmaterials. Workers removing the hazardous materials need to beprotected. Other people who must of necessity be near the work site needto be protected. For example, hazardous materials are to be removed froma portion of an airport terminal, hospital, or other site which needs tobe in continued use.

It is the usual practice to establish and continue air circulationthrough a work space during the entirety of the decontamination process.If, however, there is a failure to continue the air circulation due topower failure or mechanical problem, the prior art does not teacheffective method or apparatus to effectively seal the work space.

A long felt need exists to prevent escape of particulates from the workspace at all times, even in the event of failure to continue aircirculation during the decontamination process. In addition, a needexists for method and apparatus that is reasonably accomplished bydecontamination workers with normal materials at hand.

SUMMARY OF THE INVENTION

My invention provides for improved environment for removal of hazardousmaterials such as asbestos from contaminated spaces. My inventionprovides for pre filtration of air before entry into the work space,reduction of pressure in the work space, and filtration of the airbefore discharge into the environment. A containment of the targetedcontaminated area must be provided. Polyethylene plastic film may beused to seal and define the containment area. Filters are provided onall air inlets. A blower exhausts air form the containment area. Filtersare provided in the exhaust passage to prevent unacceptable discharge ofhazardous particulates. An airlock may be provided for access to thework space. High efficiency particulate air filters may be used in theinlet and exhaust passages.

BRIEF DESCRIPTION OF THE DRAWING

A more complete understanding of the invention may be had by referenceto the following Detailed description when taken in conjunction with theaccompanying drawing wherein:

FIG. 1 is a plan view of the embodiment of the invention.

FIG. 2 is a plan view of an alternate embodiment of the invention.

DETAILED DESCRIPTION

Referring now to FIG. 1, the preferred embodiment of the invention isillustrated. The contaminated work space 10 is sealed by existing walls,floor, ceiling, doors, and windows as far as possible. Any cracks oropenings are sealed by polyethylene plastic film, staples, tape,caulking and other means well known in the industry. For purposes ofthis specification, sealed means generally sealed as described above,but is substantially airtight, but is not absolutely airtight, allowingfor cracks, gaps, tears in polyethylene film, and the like.

A particulate filtration machine 12 contains a blower which receives airfrom the work space 10 through a filter or series of filters and thenexhausts or discharges the air to the outside of work space 10, throughan outlet 14. For purposes of this specification, outside means thespace outside the work space 10 and the sealed spaces attached thereto.

Filters 16, 18, 20, and 22 may be provided to cause air flow across allareas of the work space 10.

An accessway 24 is provided for workers to enter and exit, and to allowpassage of tools, equipment, and materials.

Accessway 24 provides a door 26 and a filter 28. The door 26 should sealvery well, airtight if possible to provide a sealed door means. Thefilter 28 should provide the required filtration of air entering thecontainment area, and should be free of any external flow restriction.

A contaminated locker room 30 is provided as part of accessway 24 forthe workers to change in and out of their work clothing as they enter ofleave the work space 10.

As herein described, a sealed doorway is defined as generally sealed, asa close fitting door, preferably with weather strip, a poly(polyethylene) film covered opening with a slit in the film and a polyfilm flap on the side upstream of air flow to cause the film flap toseal in the presence of any pressure differential of air flow toward thework space 10. A sealed doorway is intended to prevent free flow of air,but for the purposes of this specification allows small cracks, or gaps,and is not necessarily completely airtight. All sealed doorways are notonly substantially airtight, they are preferably equipped with a doorcloser, designed for the purpose or improvised.

Filters as used in this specification are defined as any of a variety offilters sufficient to trap most, if not all, of the hazardousparticulates to be removed; including, but not limited to highefficiency particulate air (HEPA) filters.

A shower room 32 is provided as part of accessway 24 for the workers totake a shower to remove particulate matter from their persons beforeleaving the work site.

A clean locker room 34 is provided as a part of accessway 24 for theworkers to leave their clean street clothing to avoid contamination ofthis clothing during their work time.

Sealed doorway 36 separates the contaminated locker room 30 from theshower room 32. Sealed doorway 38 separates the shower room 32 from theclean locker room 34. Sealed doorway 40 separates the clean locker room34 from the outside.

Optional airlock walls 46 and 48 may be provided with sealed doorways 42and 44 to provide additional doors to reduce unfiltered air flow throughaccessway 24 while personnel pass through accessway 24. Filters 28, 52,54, 56, 58, and 60 filter air as it passes through accessway 24 intowork space 10.

A particulate filtration machine 12 is installed in communication withwork space 10, shown inside the work space 10 in the drawing, but couldbe outside the work space 10 and work just as well. An outlet hose 14 issealed to work space 10 wherever the outlet hose 14 passes through thecontainment of work space 10. In this arrangement, contaminated airenters the filtration machine 12, is filtered, and moved by blowerthrough outlet hose 14 to outside the work space 10.

Referring to FIG. 2, an alternate arrangement can be used to connect theparticulate filtration machine 112 to work space 110. In thisarrangement an inlet hose 50 to the filtration machine carriescontaminated air from the work space 110 to filtration machine 112 wherethe air is filtered and moved by the blower in filtration machine 112 tothe outside environment. This arrangement is preferable where there is alimitation in size of work space 110. An accessway 124 is provided forworkers to enter and exit, and to allow passage of tools, equipment, andmaterials with the same features as accessway 24 in FIG. 1. Otherfeatures of the alternative embodiment described in FIG. 2 are the sameas described for the preferred embodiment described in FIG. 1.

Referring again to FIG. 1, asbestos abatement or other hazardousparticulate removal results must be measured against a baseline of theenvironment outside the intended work space 10. A special air samplingdevice draws a calibrated air volume through a filter pad. Phasedcontrast microscopy is then used to count the hazardous particles toestablish the baseline environment contamination.

In a decontamination project, warning signs are erected around the workspace 10; also under some conditions, barricades must be erected toestablish a regulated area.

Any heating, ventilating, and air conditioning must be turned off toprevent inadvertent activation of this equipment which would causeuncontrolled spread of hazardous particles while removal is in progress.Non-stationary items such as furniture must be removed from the workspace 10. Stationary items are decontaminated and covered withpolyethylene film and sealed with adhesive or tape.

All windows and vents are sealed with wood, poly film, tape, adhesive,etc., making surer edges and joints are sealed. A combination of polyfilm with existing walls, floors, and ceilings is used to seal the workspace 10. poly film joints are preferably overlapped at least 12 inchesand sealed with adhesive or tape. Upper ends of the poly film can beheld in place with tape, nails, tack strips, staples, adhesive, or othermeans available to the workers.

If, for example, in a refinery where accessway 24 is not feasible inconjunction with work space 10, temporary structure must be provided.Such temporary work structures may be constructed of a combination ofplywood, fiber board, scaffold, or pipe frame sealed with poly film. Itshould be recognized that hazardous materials may be present in powerplants, carbon plants and refineries and other open areas.

Referring now to FIG. 1, a project requiring removal of hazardousparticulate matter such as asbestos would have work space 10 establishedaround the contaminated area. Accessway 24 and all other features ashereinbefore described are established.

Operation of my system includes continuous operation of the particulatefiltration machine 12 before removal work is started, until all removalwork is completed, including non-working time. The bower in thefiltration machine reduces the air pressure in work space 10 belowambient air pressure. This reduced air pressure in work space 10 inducesair flow through the machine 12 filters and discharges the filtered airoutside work space 10. Air removed form work space 10 is made up by flowthrough filters 16, 18, 20, and 22 to provide flow from these filtersacross work areas in work space 10; and through filters 28, 52, 54, 56,and 60 in accessway 24. The reduced air pressure in work space 10 causesany air leaks to flow frog outside to inside work space 10; preventingflow to contaminated air in work space 10 to the outside environment.

Air flows through filter 60, clean locker room 34, filters 58, 56,shower 32, filters 54, 52, contaminated locker room 30, and filter 28into work space 10. This air flow is induced by the ambient air pressurecausing flow into the reduced air pressure in work space 10, then intofiltration machine 12 where it is filtered and the air pressureincreased by the blower to cause the filtered air to be dischargedthrough outlet 14.

Workers coming to work may enter clean locker room 34 through doors 40and 41. There they may change from their clean clothing and leave theclean clothing in locker room 34, then go through doors 44, 38, 42, and36 into locker room 30 where they may put on clothing left in lockerroom 30 previously. Alternately, they may bring a set of clean clothingto work and leave this clean clothing in locker room 34, and proceed towork in clean clothing worn to the job site.

Workers leaving the work site exit work space 10 through doors 26 and 27into contaminated locker room 30 where their contaminated clothing isremoved and placed in bags for disposition. Workers then walk throughdoors 36 and 42 into shower room 32 where they shower to removehazardous materials from themselves. Then they walk through doors 36 and42 into locker room 34 to put on clean clothing. Workers may then exitthrough doors 40 and 41. No two adjacent doors in accessway 24 should beopened simultaneously to avoid excessive passage of air through thedoors rather than -he filter in each wall adjacent the door. Forexample, doors 36 and 38 should remain closed while door 42 is open.Thus, locker room facilities are provide for the critical clothingchange and shower needed by the workers as they leave the work space atthe end of a work day.

At no time should air flow through filters 28, 52, 54, 56, or 60 berestricted. At no time should air glow through filtration machine 12 berestricted.

As stated earlier, the filtration machine should be operatedcontinuously throughout the job; that is 24 hours per day, 7 days perweek Such continuous operation will sweep throughout all the ventilatedspaces in accessway 24 and work space 10. Any particulates in thesespaces will be moved into the filtration machine 10 and trapped in thefilter.

In case of failure of the filtration machine during the progress of thehazardous material removal project, my system will still providefiltration of any air that may move through out of work space 10 becauseall provided passageways have filters to prevent exit of air containinghazardous particles. This safety feature works even if the work space 10and accessway 24 are contained in a building with separate heating,ventilating, or air conditioning system which would cause drafts or aircurrents to blow on work space 10. This safety feature works if the workspace 10 is outdoors and a natural wind blows, causing air flow throughwork space 10 since the air exiting the work space would be filtered,since all passageways are filtered.

Although a single embodiment of my invention with one variation has beenillustrated in the accompanying drawings and the foregoing DetailedDescription, it will be understood that the invention is not limited tothe embodiment disclosed, but is capable of numerous rearrangements,modifications, and substitutions of parts and elements without departingfrom the spirit and scope of the invention.

I claim:
 1. Apparatus for decontamination comprising:a sealed work spacehaving first filtered passage means for conducting air between the workspace to outside the work space, first sealed door means for access tothe work space, blower means for removing air from the work space, andsecond filtered means to filter air passing through the blower means. 2.Apparatus according to claim 1 further comprising a first airlock sealedto the work space and communicating with the first sealed door means;and a second sealed door means for access to the first airlock fromoutside, and a third filtered passage means for conducting air betweenthe first airlock and the work space, and a fourth filtered passagemeans for conducting air between the first airlock and the outside. 3.Apparatus according to claim 2 further comprising a second airlock andcommunicating with the second sealed door and the fourth filteredpassageway; a third sealed door means for access to the second airlockform; outside, and a fifth filtered passage means for conducting airbetween the second airlock and the outside.
 4. Apparatus according toclaim 3 further comprising a third airlock sealed to the second airlockand communicating with the third sealed door and the fifth filteredpassage; a fourth sealed door means for access to the third airlock fromthe outside, and a sixth filteredpassage means for conducting airbetween the third airlock and the outside.
 5. Apparatus according toclaim 3 further comprising a shower in the second airlock.
 6. Apparatusaccording to claim 3 further comprising a first partition sealed in thesecond airlock, the partition separating the main portion of the secondairlock from the first airlock, a fifth sealed door means in the firstpartition and communicating the first airlock and the second sealedairlock.
 7. Apparatus according to claim 6 further comprising a secondpartition sealed in the third airlock; the partition separating the mainportion of the third airlock from the second, a sixth sealed door meansin the second partition and communicating the third airlock and thesecond airlock, and an eighth filtered passage in the second partitioncommunicating the second airlock and the third airlock and the thirdairlock.
 8. The method of decontamination comprising the stepsof;establishing a sealed work space surrounding the hazardous materialsproviding filtered inlet air passages, blowing air from the work spaceto outside the work space, filtering the air blown from the work space,whereby leakage of air to the work space will be from outside into thework space, and whereby failure to maintain the step of blowing air willstill provide filtered air between the work space and outside the workspace.
 9. The method of claim 8 further comprising the step ofprovidinga first airlock with a first sealed door and a first filtered passagewaysealed to and communicating with the work space.
 10. The method of claim9 further comprising the step ofproviding a second airlock with a secondsealed door and a second filtered passageway sealed to and communicatingwith the first airlock, first filtered passageway and the work space.11. The method of claim 10 further comprising the step ofproviding athird airlock with a third sealed door and a third filtered passagewaysealed to the second airlock and communicating with the first and secondairlocks, first and second filtered passageways and the work space. 12.The method of claim 9 further comprising the step of providing a showerin the second airlock.
 13. The method of claim 11 further comprising thesteps of providing clothing changing facilities in the first and thirdairlocks.